1. Field of the Invention
Example embodiments of the present invention generally relate to a semiconductor chip package and a mounting structure thereof. More particularly, the present invention relates to a BGA semiconductor chip package and a mounting structure thereof.
2. Description of the Related Art
A ball grid array (BGA) package may include external connection terminals, for example, solder balls, distributed over a surface of the package. The BGA package was developed in response to increased integration of semiconductor devices and increased number of I/O pins. The BGA package may have a reduced mounting area and/or improved electrical characteristics.
BGA packages may be categorized as a solder mask defined (SMD) type or a non-solder mask defined (NSMD) type. As illustrated in FIG. 1, a SMD type BGA package 510 may include ball land pads 524 defined by a solder mask 527. As illustrated in FIG. 2, an NSMD type BGA package 610 may include ball land pads 624 spaced from a solder mask 627.
Compared with the NSMD type BGA package 610, the SMD type BGA package 510 generally has a larger contact area for solder balls 551 with a substrate 520, and thereby, generally has relatively strong resistance against external shock. However, the SMD type BGA package 510 generally has a smaller contact area for the solder balls 551 with the ball land pads 524. In some instances, problems, for example, solder joint cracks and package cracks (C and A, respectively, in FIG. 1) may occur in the SMD type BGA package 510.
Compared with the SMD type BGA package 510, the NSMD type BGA package 610 may have a larger contact area for solder balls 651 with the ball land pads 624, which may improve electrical characteristics. However, the NSMD type BGA package 610 generally has a smaller contact area for the solder balls 651 with a substrate 620; which may mean the NSMD type BGA package 610 has a relatively weaker resistance against external shock. In some instances, problems, for example, peeling D of the ball land pads 624 and package cracks B may occur.
As described above, the SMD type BGA package 510 and the NSMD type BGA package 610 may both have weaknesses. These weaknesses may cause problems, for example package cracks A, B solder joint cracks C, and/or peeling D. In the case of a package having a tape wiring substrate chip, during a bending test or handling by an operator, mechanical stresses may generate cracks A, B in areas where solder balls are not formed.
As a result, as shown in FIG. 3, an underfill resin 697 may be used between the NSMD type BGA package 610 and a mounting substrate 690. However, the use of the underfill resin 697 may result in an increase in manufacturing cost. In addition, the underfill resin 697 may make the package more difficult to repair.
Also, when the SMD type BGA package 510 is mounted on a mounting substrate 590, the height of the solder balls 551 may decrease, as illustrated in FIG. 4. For example, a height of solder balls 551 with a diameter of 450 μm is between 340 μm and 350 μm. After the package 510 is mounted on the mounting substrate 590, the height of the solder balls 551 may be decreased to between 270 μm and 300 μm. The decrease in height reduces the space between the SMD type BGA package 510 and the mounting substrate 590. Heat, which is generated by a chip mounted on the SMD type BGA package 510 during operation, may be trapped in the reduced space between the SMD type BGA package 510 and the mounting substrate 590. The resulting thermal stresses may also cause solder joint cracks.
One conventional method to solve these problems, using nonfusible balls 752, is illustrated in FIG. 5. The nonfusible balls 752 do not melt during a soldering reflow process. The nonfusible balls 752 may help the BGA package to maintain the height of the solder balls 751.
Although the technique disclosed in the BGA package 710 is generally acceptable, it is not without shortcomings. For example, the BGA package 710 may require an additional process to form the nonfusible balls 752. This may lead to a more complicated manufacturing process. In addition, because the nonfusible balls 752 are connected to connection pads 793b of a mounting substrate 790, the connection pads 793b must be considered when designing wiring patterns for the mounting substrate 790. Further, package cracks may still occur at areas where the solder balls 751 and/or nonfusible balls 752 are not formed.